Homeowrk 2 KEY - Answers to Homework Set #2 1. Some of the...

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Answers to Homework Set #2 1. Some of the major limiting factors and possible solutions are suggested in the following table: Limiting factors Possible solution 1 Plants absorb red & blue light well, but not green or near- infrared light. About half of the incident energy of sunlight is not absorbed. Replace the chlorophyll in one of the photosystems by bacteriochlorophyll, which absorbs longer wavelengths, or by a modified chlorophyll that absorbs at shorter wavelengths. 2 Because the antennas of photosystem I and Photosystem II have similar (though not identical) absorption spectra, they compete for the same photons. Same as for 1. You also could consider engineering a photochemical apparatus that used only a single photon to move an electron all the way from H 2 O to NADPH, H 2 , or another low-potential product. Red photons have just enough energy to do this. 3 The photochemical electron- transfer reaction occurs from the lowest excited singlet state of a chlorophyll complex. If higher energy (blue) photons are absorbed the extra energy is lost as heat. Same as 1 and 2. 4 At high light intensities, the antenna system absorbs light faster than reaction centers can use the energy. The extra photons are wasted. Increase the ratio of reaction centers to antenna pigments (decrease the size of the antenna). (Why would this not be as useful in Seattle as in Arizona?) 5 Because Rubisco has a low turnover number, carbon fixation can not keep up with the reactions driven by light.
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This note was uploaded on 02/02/2010 for the course BIOCHEMIST Biochem 44 taught by Professor Parson,young during the Winter '10 term at University of Washington.

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Homeowrk 2 KEY - Answers to Homework Set #2 1. Some of the...

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